There are a number of Lychnis including pinks, whites and magentas. Also called Rose Campion, we always called them Mullein Pinks. Pretty much cast iron plants just cannot be killed. They are not exactly invasive though. Lychnis Chalcedonia is known as Maltese Cross in various shades of orange. I had Grammie's plants here, but they have seeded together with the ones that were already here. There was an inquiry about this plant. Is it invasive?
Well, the stand you see here has been there since I moved here some ten years ago. In that time the stand has doubled. They spread by seed and it does produce plenty of it. It was in my grandmother's garden for sixty years and never seemed to be there in any overpowering quantity